Conversion of methyl formate to acetic acid



Patented May 23, 1950 ednveasibs 'oii methane ACETIC ACID waltei flnrifGr'oombridge, s amina-{heath England, assignor to Celanesef Corporation "of America; a 'corporati'owof "Delaware whims-g; Appmatin Api'il miia'siai organic communes, and j s more fparticularly co'nc'e'r'n'ed with'--the'= manufacture of acetic acid:

According-to the present intentionracetic acid is manufactured lay-subjecting methylformate' to the action of heat- "in "the i presence of certain catalysts com'prisingffcarbonylaforming metals or compounds together yvithf halo'gensr The cataly'sts' which jare used in"ca' rr ying' out 'f' the process of th'e' intention-"may consist of one or moreor theiron metalstogether'with" ahalogen in the free state or in the form of a compound which is I capable of yielding free halogen under-the reaction conditions?" Of the iron metials; niokelhas been found; 'to*"give the "best re-" suits. Thehaiogenmay-be'used wholly'or partly in combination with nickel, especially as" a hy-' drated halide, e. g. Ni I .6 I- I2Q, orin theform of another metal 'COillpOfl nd' iSuCh fiS copper iodide, an{ organic halogen compound suchfas an 'alkyl iodideie'. gsmethyl iodide pr in the form of hydroge'n iodide. Alternatively, the "free halogen maybe used as such I Of the? halogens, iodine has been found tofbe the' mostefiectivej although bromine or chlorine-may be used desired;

In addition to the iron metalslfcertain other metalsfandfin particular"tungstenfand metal of the "fifth" group of the iPi-Zi'lqdifi' "systemf'namely vanadium} antimony"and bismuthi'have a1so been found td-behse'fulfirith processor the invention'fbu't their activity" is verygreatlyfenhanced by the presence of a metal ofthirdri'grbup. Thus; a trace of'ni ckelmakes' those metals highly active""-'in"thefprocessfso that; for "example; the

catalyst "used may consist oftungsten "together with an-iodidaeig. copperiodide, and a trace of nickel-H While the metalflmay be introduced into the reaction zone as 'a compound "with the halogenit' may; if desi'red'rbe wholly Or partly introduced as a carbonyl especiallywhere'nickel is used asa component-of the catalyst;

The quantity of catalyst used where the catalyst is NiIz.6I-I2O may in'generalamount to from v 1 to'10% of theweight'of the'methyl formateor even more, although it is usually uneconomical to employ more; than 157a by weightandgenerally quite satisfactory results are obtained when using much smaller quantities',jfe, g. quantities not? excedingi 5% of the weight of the methyl formate." wherepthersubstanoes are use a catalyst equivalent'quantitiesofmetal and halo genmay be employed?""It'shouldbepointed out,

however, that it is not necessary that the metal and halogen should be employed in stoichiometrical portions, for example it has been found that 56' '7 actually employed a "imieem "proportion of m when using "nicliluas when using sub:sta' ntiallyjle' or oreven 1ess th an that"represente'd" by this forniulai The reaction is preferably-carried out at tem-' formate togetherw h' afsma' sired cata ial a limits, forfi ins'tance' quantit ie eq alto up 1704 or o vn ?P o 'per. yYfOrmate'Qmay bef "h adi .1 molecular,proportiofi'per more ula'rpi'oportion'of methyl' format'e seems to lbfir l ttl advantage? and'unduly'dilutesfthea t1 acid produced" tie is advan- V k ncreased yields and co versions appar'entlyby uppressing ineth- I ane" andearb'on 'dioifide 'foi'rnltidn from theg'i gnethyl formate used as starting material; About;

used, I se quantities 'lfhe presence of ca w' g ts r s nce. or 'u 1 molecular proportion of I h i y Iormatefjis sum molecular proportion pf m n o thi pu e; but aj a' g r' qu m f be 'usedr rt mafly whenimethanol ispresent the methanol. andcarbonipo xidefin this case;- "reacting to'form additional a a A I Acetic acid, methyl ac'ett' or] inert hydrocar-{ bons may be present'in'the'reaction' zone and may" i6 acid.

act as reaction medium, particularly where the: process is operated continuously. For instance, the reaction may be carried out in a column of;

. w iy iim th f with'ffree iodine-excellentfresult' ca "be 'obtaine'di mum thancorre-} sponds to the iorlnul N112 quantityof iodine toi otmo 'ethani methyl formate and may be maintained at this value throughout the process, but here again the quantity used may be modified if desired, espef 7 cially where methanol is present in the reactants together with methyl formate. .The process of the invention may also be carriedout continu-- ously in the gas phase.

The methyl formate to be used in theprocess of the invention may be obtained very conveniently by isomerisation of formaldehyde, for example by heat treatment under alkaline conditions. By combination of this process with the process of the invention there is thus provided a method of converting formaldehyde directly into the more valuable aceticacid.

which comprises heating methyl formate in the presence of nickel carbonyl and iodine.

3. Process for the manufacture of acetic acid, which comprises heating methyl formate together with nickel iodide hexa-hydrate to form acetic acid under the catalytic influence of nickel carbonyl and iodine produced in'the reaction zone.

4. Process for the manufacture of acetic acid,

which comprises heating methyl formate at a. temperature of 300 to 400 C. and under a pressure of more than 100 atmospheres in the presence of nickel carbonyl and iodine.

V 5. Process for the manufacture of acetic acid, fwhich comprises heating methyl formate at a .temperature of 300 to 400 C. and under a pressure of more than 100 atmospheres together with nickel iodide hexa-hydrate to form acetic acid under the catalytic influence of nickel carbonyl The following examples illustrate the invention:

. Example 1 Methyl formate and 'water'in equiinolecular proportions, together with 0.14 molecular proportion of NiI2.6H2O per molecular proportion'of" methyl formate, are charged into an autoclave of sufiicient capacity to provideasubstantial vapour space above the liquid chargeyfor example, the vapour space may be equal to some four times the volume of the liquid charge- The autoclave is closed and heated to a temperature of 335 C. and maintained at this temperature for 1% hours. Under these conditions a pressure of some 300 atmospheres develops which falls' substantially when the products are allowedto cool.

On opening the autoclave a certain amount of gaseous products including methane'and carbon dioxide are released to leave an aqueous liquid containing acetic acid, formic acid and methyl acetate which are separated by fractionation.

Example 2 An autoclave is charged with equimolecular proportions of methyl formats, water and carbon monoxide, together with nickel carbonyl and iodine in the'molecular proportions of 1.5% and 0.4% respectively based on the methyl formate. As in Example 1 an autoclave is used which provides adequate vapour space. The autoclave is closed and heated to 335 C. for 1% hours and thereafter cooled and'opened and the products, consisting of acetic acid,'m ethyl acetate and some formic acid, separated by fractionation.

In this case substantially less methane and carbon dioxide was produced and both the yield and conversion were substantially higher than in Example 1. n I

Having described my inventiomwhat I desire to secure by Letters Patent is:

1. Process for the manufacture of acetic acid, which comprises heating methylformate in the presence of a carbonyl of an iron metal and a halogen selected from the group consisting of chlorine, bromine and iodine.

2. Process for the manufacture of acetic acid,

and iodine produced in the reaction zone.

6. Process for the manufacture of acetic acid, which comprises heating methyl formate together with water at a temperature of 300 to 400 C. and under a pressure of more than atmospheres in the presence of nickel carbonyl and iodine.

7. Process for the manufacture of acetic acid, which comprises heating methyl formate with water at a temperature of 300 to 400 C. and under a'pres'sure of more than 100 atmospheres together with nickeliodide hexa-hydrate to form acetic acid under the catalyticinfiuence of nickel carbonyl and iodine produced in the reaction zone.

8. Process for the manufacture of acetic acid, which comprises heating methyl formate together with carbon monoxide at a temperature of 300 to 400 C. and under a pressure of more than 100 atmospheres in the presence of nickel carbonyl and iodine. f

. QJProcess for the manufacture of acetic acid, which comprises heating methyl formate with carbon monoxide at a temperature of 300 to 400 C. and under a' pressure of more than 100 atmospheres together with nickel iodide hexahydrate to form acetic acid under the catalytic influence of nickelcarbo'nyl and iodine produced in the reaction zone. V 7

10. Process for the manufacture of acetic acid, which comprises heating methyl formats together with water and carbonmonoxide at a temperature of 300 to 400 C. and at a pressure between 200 and 400'atmospheres in the presence of nickel carbonyl and iodine. V I

11. Process for themanufacture of acetic acid, whichcomprises, heating methyl formate with water and. carbon monoxidefat a temperature of 3'00'to 400 C. and at a pressure between 200 and 4001atmospheres together with nickeliodide hexahydrate to form acetic acid'under the catalytic influence of nickel carbonyl and iodine produced .in the reaction zone.

WALTER rrsunroaoommncm REFERENCES CITED file of this patent: V

UNITED s'ra'rns PATENTS 2,457,204 Brooks Dec. 28, 1948 The following references areofrecord in the 

1. PROCESS FOR THE MANUFACTURE OF ACETIC ACID, WHICH COMPRISES HEATING METHYL FORMATE IN THE PRESENCE OF A CARBONYL OF AN IRON METAL AND A HALOGEN SELECTED FROM THE GROUP CONSISTING OF CHLORINE, BROMINE AND IODINE. 